The Pacific Ocean has an area of roughly 156 million sq km (60 million sq mi) and contains more than 30,000 islands. The Pacific Ocean total are exceeds that of all the land masses combined. While the total land area, of all the islands amounts to only one-quarter of one percent of the ocean's surface area. The largest islands, in the western region, form volcanic island arcs that rise from the broad continental shelf along the eastern edge of the Eurasian Plate. They include Japan, Taiwan, the Philippines, Indonesia, New Guinea, and New Zealand.

The oceanic islands, collectively called Oceania, are the tops of mountains built up from the ocean basin by extruding molten rock. The mountains that remain submerged are called seamounts. In many areas, particularly the South Pacific, the land features above the sea surface are accretions of shell material (see Coral Reef).

Along the eastern edge of the Pacific, the continental shelf is narrow and steep, with few island areas. The major groups are the Galápagos at the equator, which rise from the Nazca Plate, and the Aleutians in the north, which are part of the North American continental shelf.